Treatment of hydrocarbons



'y Patented 6,1945 j TREATMENT or mmnocAnBoNs I Raymond C. Archibald,Berkeley, Calif., assigner to Shell DevelopmentCompany, San'Francisco,Calif., a corporation of Delaware Application November 2, 1942, SerialNo. 464,289

11 claims. This invention relates to an improvement in the catalytictreatment ofhydrocarbons boiling in the gasoline boiling range withsulf-active catalysts consisting essentially of pilled dehydrogenatingmetal sulfides. More particularly,

the. invention relates to a method for increasing the eii/ective life ofthe catalyst in said processes by a periodic treatment of the catalystin situ.

As is known, there is a great demand for an economical and` practicalprocess for the catalytic dehydrogenation of the lighter hydrocarbonssuch as hydrocarbons boiling within the gasoline boiling range. Most of.the hydrocarbon materials which it is desired to treat by catalyticdehydrogenation are derived from petroleum and/or coal tar distillatesand contain from traces to appreciable amounts of sulfur compounds. Apractical catalytic process suitable for use with these hydrocarbonmaterials therefore lrequires the use of a sulf-active catalyst. Manyprocesses have been developed wherein these various hydrocarbonmaterialsare treated. using dehydrogenating metal oxide catalysts. In general,the dehydrogenating metal oxides are very active dehydrogenatingcatalysts at elevated temperatures and are employed -in relatively smallamounts supported upon major amounts of suitable adsorptive carrierssuch, in

particular, asactive alumina. Some of these K proposed processes aresuitable for certain-applications. All of them, however, have the greatdisadvantage that theyrequire so-called short and costlylbut materiallydecreases the production` capacity,A per catalytic converter.Furthermore, the periodic regenerationby burning carbonaceous depositswith air subjects the apparatus to frequent temperature change andalternate oxidizing and reducing conditions. This requires that theseprocesses be effected in apparatus constructed of special steels oralloys. The rate of deposition of. carbonaceousn materials upon thecatalyst in certain processes can be repressed to' a certain extent' bythe use of hydrogen pressure. This, however, is generally consideredimpractical inasmuch as under high hydrogen pressures thedehydrogenation reaction is usually considerably repressed. Onthe lotherhand, very excellent sulf-active catalysts which may be appliedundervery high hydrogen pressures have been developed particularly roruse indestruc-- tive hydrogenation ofA higherfboiling hydrocarbons. One typeoi such catalysts consists essentially of a mixture of metal sulfldes.Under (CL 19e-5o) conditions for which these catalysts were inl tended,that is, for. destructive hydrogenation, considerable hydrogen pressuresprevail and there is little deposition .of carbonaceous mate-q, rial.Consequently, under .these conditions-these catalysts have a very longactive life. Further- `more, in the destructive hydrogenation when thecatalyst is iinally spent, the valuable components are recovered and'regenerated. The regeneration in this case is, however, not similar tothat employed in the above-mentioned oxide type catalyst but consists inan entire remaking of the catalyst.

It is found that the above-described sulf-active catalysts are verysuitable for the catalytic devhydrogenation of lighter hydrocarbons, forexample, dehydrogenatable hydrocarbons yboiling in the gasoline boilingrange. In the use of these catalysts for this purpose, dehydrogenationrather than hydrogenation conditions prevail, carbonaceous 'materialsgradually deposit upon the catalyst, and in time the dehydrogenationactivity of the catalyst declines. Since, however, in thedehydrogenation of such hydrocarbons with catalysts of this type certainquantities of hydrogen, for instance 1 to 50 atmospheres, are suitablyemployed, the deterioration ofthe catalyst by carbonaceous deposits isvery slow. These catalysts may therefore be employed for the de- 30hydrogenation of these hydrocarbons over relatively long periods, forinstance 400 hours, before regeneration of the catalyst is necessary.This, it will be seen, is a distinct:l advantage over the use of theabove-described oxide type catalyst.

These snif-active metal sulde catalysts can be applied to carriermaterials, as described, for the oxide type catalysts and, in suchcases. can -be-regenerated by conventional means, thatv is, by burningoil the carbonaceous deposits with air. 40 During such regeneration,however, the metal suldes are converted to the corresponding oxides andafter .the lcarbonaceous deposits have y been removed-it is necessary tosubject the catalyst to a thorough sulfurization. This latter step isoften diiiicult and costly. These sulf-active metal sulfide catalysts,however, are not as' active as the corresponding oxide catalysts fordehydrovated. The usualmethods involving burning on of the carbonaceousdeposits with oxygen or owgen-bearingv gases cause the pellets to losestrength and crumble. Oxygen-containing gases oriljsuch as air. stomste.are furthermore unsuit 5 lytic -dehydrogenation could be readilyreactiis advantageous.

` able for the reason that they convert the metal suldes to thecorresponding metal oxides.

In copnding application Serial No. 434,893, filed March 16, 1942, ofwhich the present application is a continuation-impart, there isdescribed and claimed a method whereby these pelleted metal suliidecatalysts may be advantageously reactivated. According to the methodmore fully described in said copending application, catalysts consistingessentially of the above-described dehydrogenating metal suldes', whendeactivated in the catalytic dehydrogenation of hydrocarbons, areadvantageously reactivated in situ by treatment with sulfur dioxide.Whereas regeneration by oxygen causes the catalyst pellets toimmediately crumble, repeated reactivation of the catalyst with sulfurdioxide leaves the pellets substantially unaffected in physicall shapeand strength. Furthermore, the use of sulfur dioxide to reactivate theabove-described suliide catalysts does not cause substantial oxidationof the metal suliides and does not require a subsequent re-sulfurizationof the catalyst. Furthermore, the reactivation of these catalysts withsulfur dioxide is very effective, may be effected in a very short time,and does not require substantial change in the temperature conditions inthe reactor.

It is now found that a gas mixture comprising sulfur dioxide andhydrogen sulfide is particularly excellent for eiecting thereactivation. In the use of such gas mixtures all danger of oxidation ofthe catalyst or the reactor walls is eliminated. Also, due largely tothe large heat capacity of hydrogen suliide, the reactivation may beeected at a more rapid rate without causing deterioration of thecatalyst by local overheating. Furthermore, as will be described in moredetail below, mixtures comprising these gases which are particularlysuitable may be easily obtained as a by-product from'the conversionprocess.

The present activation treatment is applicable to any of the pelleteddehydrogenating metal sul-` de catalyst of the above-'described type. Itis especially suitable for the treatment of dehydrogenating metalsulfide catalysts consisting essentially of a sulde of a metal selectedfrom Group VI of the Periodic System and a sulfide of a metal selectedfrom Group VIII of the Periodic System. For example. it is especiallysuitable for use with catalysts consisting .essentially of a pelletedmixture of tungsten sulfide and nickel sulide. These metal sulfides whenpelleted inthe pure form often yield hard strong pellets having ametallic luster. In certain cases. however, the use of a small amount ofone of the many known binders Also, the dehydrogenating metal sulfide ormixture of such suldes may be pelleted in admixture with a minor amountoi a relatively inert material such as a powder of alumina. kieselguhr,clay or the like. In the apjpended claims when referring to thesecatalysts'` the expression consisting essentially oiis not meant toexclude minor amounts of such extenders in the catalyst pellets.

These catalysts are especially suitableand may.

be employed for the dehydrogenation of dehydro- -genatable liquidhydrocarbons boiling in the gasoline boiling range such, inparticuiar,as -n aphthenic lhydrocarbons and naphthenic gasoline fractions.Suitable conditions applicable for the vlo catalytic treaiient otthesevarious hydrocar-Q- of this type are, i'or example. approximately asfollows:

Temperature C 425-525 Total pressure atm lil-5G Ratio of hydrogen tohydrocarbon feed mois/mol-- 2-20 Liquid hourly space velocity 0.5-5After the catalyst has been used on-stream for some time the activitygradually declines to a point where it is desirable to subject it to aregeneration or reactivation treatment. The hydrocarbon feed isdiscontinued and excess hydrocarbons purged from the catalyst,preferably with hydrogen or with an inertgas. The catalyst activity isthen restored by a treatment with a gas mixture comprising sulfurdioxide and hydrogen sulfide. The ratio of sulfur dioxide to hydrogensulfide in the gas mixture may vary widely. Even a small amount ofhydrogen sulfide in the sulfur dioxide is sufcient to prevent oxidationof the catalyst by any contaminating air or oxygen. Larger amounts allowthe gas mixture to be passed through the catalyst bedat high 4rateswithout danger of overheating the catalyst.

Also, the gas mixture may contain one or more inert gases such asnitrogen, carbon dioxide or the like. Very suitable gas mixtures may, ifdesired, be prepared by burning hydrogen sulfide with an insufcientamount of air. The concentration oi hydrogen sulfide and sulfur dioxidein the gas vmay be adjusted and controlled by adjusting and controllingthe concentratiomof oxygen in the oxygen-containing gas, for instance,

by adding a diluent to air, and by adjusting and.

controlling the ratio of hydrogen suliide to oxygen-containing gas.Also, if desired, the concentrations of sulfur dioxide and hydrogensulfide in the combustion gases may be reduced to any desired lowconcentration by adding a diluent gas. such as recycled spentregeneration gas, .flue gas,

or the like. This can also be effected, if desired,-

by burning a suitable quantity of a hydrocarbon such as natural gas withthe hydrogen sulfide.

The time required for the reactivation treatment depends upon severalfactors such, in particular, as the amount of catalyst, the length ofthe catalyst bed, the concentration of sulfur di- 1 oxide in the gasmixture, the rate of addition of-the gas mixture, and the temperature.One ofthe advantages of the present process, however, is that theactivation may be eiected in a very short time. Thus, the reactivationrequires, in general, only a fraction of the time required to regenerateoxide catalysts with oxygencontaining gases. For example, converters ofconventional size and design may usually be' reactivated in one-half tofour'hours. Longerperiods of reactivation such as ve to ten hours are,however, in no way detrimental. During reactivation treatment verylittle sulfur dioxide is usually found in the exit gas. When the sulfurdioxide passes through the catalyst mass and appears in .the exit gasthe reactivation is usually substantially complete. A

The reactivation of the above-described pelleted catalysts according tothe present process is exothermic. When applying the process to largemasses of the catalyst the rate of passage of the gas mixture throughthe catalyst bed is therefore controlled to avoid deactivation of thecatalyst by local overheating.

A great advantage of the present process is bcn; a/nd/cr hymocgrbonmixtureswith` 55mg 7gg-.that the reactivation may be eiiected in situover -a wide range of temperatures.`

" causes lowered conversions.

The reactivation according to the present process may therefore bevconveniently eiected at the temperature at which the catalyst isemployed in the dehydrogenation. Thus, for example, when effecting thedehydrogenation process in the abo-mentioned temperature range of 425C.525 C., the reactivation may be eiected at the reaction temperature.Thus, the delaysl in bringing the reactor from the reaction temperatureto a different reactivation temperature, and vice versa, are avoided.Also, the cost of heating and cooling and the detrimental effect ofsubstantial temperature changes on the reactor and the catalyst areavoided. 'I'he temperature of the reactivatfon may, howeverr if desired,be above or below the The maximum reactivav reaction temperature. tiontemperature depends upon the thermal stability of the catalyst. Withmost catalysts o1' the type inquestion, temperatures up to about 750 C.may be applied.. In general, however, no advantage 'is gained inapplying temperatures above about 600'C. The minimum applicabletemperature also depends somewhat upon the catalyst. In the reactivationof the spent catalyst described inconnection the description of `anoperation within the scope of the invention.

Referring to the drawing, the hydrocarbon feed to be treated, 'forinstance a mixture of a'straight run naphthenic gasoline fraction and anolnic reformed gasoline fraction, said mixture containing about0.1%-0.5% sulfur, is passed vialine I to a coll 2 in furnace 3 whereinvit is vaporized and heated to a suitable temperature. Recycle hydrogenis preheated in coil 4 in the furnace and then mixed with thehydrocarbon vapors in a ratio'oi, for instance, about 3:1 to 7:1. Theterny peratures of the hydrocarbon vapors and recycled 'hydrogen areadjusted such that the mixture is at' about the Vdesired reactiontemperature, for instance 430 C.500 C. The mixture oi' hydrogen and`hydrocarbon vapors under a .pressure of, for instance, 600-700 p. s. i.passes via line 5 to a series of catalytic converters 6 and 1 the liquidhourly space velocity of the hydrocarbon being, for instance, betweenabout 1 and 4.

. .(Liquid hourly space velocity, for the purpose of with the sulfurdioxide-hydrogen sulde mixture,

a pronounced heat eiect is observed. The minimum applicable temperatureis the lowest temperature above 400 C. at which this heat effect isobserved. In case itis desired to eiect the reactivation at the lowestpossible temperature, the gas mixture may be passed through the catalystmass at a low temperature and the temperature gradually raised until theheat effect is observed. The reactivation is, in general, preferablyeii'ected at temperatures above 400 C. where the reactivation isconsiderably faster.

'I'he reactivation may be effected at any desired pressure. Ordinarypressures are, however, quitesuitable and little advantage is gained inapplying higher pressures.

As mentioned above, very suitable gas mixtures comprising sulfur dioxideand hydrogen sulfide `may be' advantageously obtained as byproducts ofthe process. As pointed out, most of the hydrocarbonaceous materialswhich it is desired to treat with the above-described catalysts containfrom small to appreciable amounts of sulfur compounds'. Under thereaction conditions employed a considerable proportion of the sulfur isconverted to hydrogen sulfide. This hydrogen sulfide which forms in thereaction accumulates in/the recycled hydrogen. Ajsmall.

amount of hydrogen sulfide in the recycled hydrogen is usually notdetrimental and may in some instances be beneiicial. concentration ofhydrogen sulfide in the recycled hydrogen, however, is detrlmentalsinceit This hydrogen sulde may be advantageously recovered from the recycledhydrogen, thereby maintaining the conversion at an optimum level.Furthermore, the

recovered hydrogen suliide may be burned with an insumcient amount ofoxygen to produce a gas mixture .comprising sulfur dioxide and hydrogensulfide, which gas mixture is particularly excellent for effecting thereactivation of the catalyst.

' One application of this modication of the process of the invention isillustrated in the at-f tached drawing wherein there is shown by meansot conventional iigures not drawn to scale one assembly of apparatuswherein the process may be advantageously applied. The drawing will beAny appreciable the present description, is defined as the volumes `ofhydrocarbon feed, measured as a liquid, passed through a given volume ofcatalyst per hour.) The converters 6' and l are filled with suitablysupported beds of a sulf-active metal sulfide catalyst, for instance,consisting essentially of an intimate mixture of 2 mol par-.ts of nickelsulfide and 1 mol part of tungsten sulde, preferably in the form ofpellets. i The reaction mixture of hydrocarbon vapors and recycledhydrogen, after y passing through the first bed of catalyst, arewithdrawn via line', passed through heat exchanger 9, and thenpassed-through converter 1. The reaction mixture is withdrawn fromconverter 'l via line M, passed through heat exchanger l2,

Acondenser i3, and then passed to a separator I4,

wherein the'liquid hydrocarbon product is separated from the gaseousfraction consisting mostly of hydrogen. The liquid hydrocarbon fractionis withdrawn via line i5. The gaseous fraction contains hydrogen sulfideproduced by desulfurization of the hydrocarbon charge. This fraction iswithdrawn via, line I6 and treated to separate the hydrogen sulfide.This may be effected in a number of known manners. One excellentmethod-is, for example, by means of the Shell Phosphate Process (seeRener and Natural vGasoline Manufacturer, September 1941). Thus,

the gaseous fraction is scrubbed with a potassium phosphate solution ina scrubber il'. consisting mainly of hydrogen from which hydrogensulfide has been substantially removed is recycled via-line i8 andcompressor i9 to the heating coil i and back to the process. Line' 2| is.or directed to aunit not shown. Hydrogen sulde gas from the stripper 25and/or from the accumu- 1ator42'l is passed via,line 28 to a sulfurdioxide. generator 29 wherein itis burned with air or oxygen introducedvia line 3l. The ratio of hydrogen sulfide to air or otheroxygen-containing sas- The gas ,hydrocarbons boiling in applied isadjusted such that after combustion there is an excess of hydrogensulfide. The gas mixture comprising, for example, 5% sulfur dioxide and4% hydrogen sulde is passed via compressor 32, line 33, and heatexchanger 36 to line n 5 leading'to converter 6. The ,exit vapors fromconverter 6 may be withdrawn via line 31 or may, if desired, be passedthrough converter l. A separate portion of the gas mixture. is passedvia line 38, line 8 and heat exchanger 9 to converter m '1. The eiiluentgas may he withdrawn via line 39.

The assembly of apparatus illustrated in the drawing and described abovemay be modified in many ways. Thus, for example, three or moreconverters may be applied either in series or in 5 parallel, or two ormore separate banks of converters may be used. Also, converters ofvarious designs may be employed and the exchanger 9 may sometimes beeliminated. If desired, the

combustion of the hydrogen sulfide may be ef- 2U fected under pressure.Also, it may be effected continuously, if desired, and the gas mixturestored in an accumulator vduring the processing. Other variations andmodifications will be apparent to those skilled in the art.

I claim as my invention: A

1. In a process for the catalytic treatment of hydrocarbons boiling inthe gasoline boiling range with the aid of a sulf-active catalystconsisting essentially of pellets of dehydrogenating metal sulfide, theimprovement which comprises periodically restoring the activity of thecatalyst by treatment with a gas mixture comprising suliur dioxide andhydrogen sulfide at a temperature between about 400 C. and 600 C.

2. In a process for the catalytic treatment of hydrocarbons boiling inthe gasoline boiling range with the aid of a sulf-active catalystconsisting essentially of pellets of an intimate mixture ofV a suliideof a metal of Group VI of the 40 Periodic System and a sulfide of ametal of Group VIII of the Periodic System, the improvement whichcomprises periodically restoring the activity of the catalyst bytreatment with a gas mixture comprising sulfur dioxide and hydrogensulv4,5

fide at a temperature between about 400 C. and 600 C. i

3. In a process for the catalytic treatment of hydrocarbons boiling inthe gasoline boiling range with the aid of a sulf-active catalystconsisting essentially of pellets of an intimate mixture of tungstensuliide and a sulfide of a metal -of Group VIII of the Periodic System,the improvement which comprises periodically restoring the activity ofthe catalyst by treatment with a gas mixture comprising sulfur dioxideand hydrogen sulfide at a temperature between about 400 C. and 600 C.

4. In a process for the catalytic treatment of the gasoline boilingrange with the aid of a sulf-active catalyst consisting essentially ofpellets of an intimate mixture of tungsten-suliide and nickel sulfide,the

improvement which comprises periodically restoring the activity of thecatalyst by treatment with a gas mixture comprising sulfur dioxide andhydrogen suliide at a temperature between about 400 C. and 600 C.

5. Ina process for the catalytic treatment of hydrocarbons boiling inthe gasoline boiling range with the aid of a sulf-active catalystconsisting essentially of pellets of an intimate mixture of callyrestoring the activity of the catalyst by treatment with a gas mixturecomprising sulfur dioxide and hydrogen suliide at a temperature betweenabout 400 C. and 600 C.

6. In a.process for the catalytic treatment of hydrocarbons boiling inthe gasoline boiling range with the aid of a sulf-active catalystconsisting essentially of pellets of dehydrogenating metal sulfide, theimprovement which comprises periodically restoring the activity of thecatalyst by treatment at a temperaturebetween about 400 C. and 600 C.with a gas mixture `comprising sulfur dioxide and hydrogen sulfideproduced by burning hydrogen sulde with an insumcient amount of oxygenfor complete combustion.

7. In a proeessfor the catalytic treatment of a sulfur-bearinghydrocarbon fraction boiling in the gasoline boiling range with the aidof a sulfactive catalyst consisting essentially of pellets of ydehydrogenating metal suliide wherein hydrogen is recycled through thereaction zone, the improvement which comprises continuously separatinghydrogen suliide from the recycled hydrogen and periodically restoringthe activity of the catalyst by treatment at a temperature between about400" C vand 600 C. with a gas mixture comprising sulfur dioxide andhydrogen suliide produced by burning said separated hydrogen suliidewith an insufiicient amount of oxygen for complete combustion.

8. The process for restoring the dehydrogenat- 5 ing activity of asuit-active catalyst consisting essentially of pellets of.dehydrogenating metal sulde which has been deteriorated by non-halogencontaining deposits, which comprises treating said catalyst with a gasmixture comprising sulfur dioxide and hydrogen sulfide at a temperaturebetween about 400 C. and 600 C.

9. The process for restoring the dehydrogenating activity of asnif-active catalyst consisting essentially of pellets of an intimatemixture of a sulfide of a metal of Group VI of the Periodic System and asulfide of a metal of Group `VIII of the Periodic System which has beendeterior- 1 ated by non-halogen containing deposits, which comprisestreating said catalyst with agas mixture comprising sulfur dioxide andhydrogen sulde at a temperature between about 400 C. and

10. The process for restoring the dehydrogenating activity of asulf-active catalyst consisting essentially of pellets of an intimatemixture of tungsten suliide and a sulde of a metal of Group VIII of thePeriodic System which has been deteriorated by non-'halogen containingdeposits, which comprises treating said catalyst o with a gas mixturecomprising sulfur dioxide and hydrogen sulfide at a temperature betweenabout 400 C. and 600 C.

11. The process for restoring the ydehydrogenating activity of asuit-active catalyst consisting essentially of pellets of an intimatemixture oi' tungsten sulfide and nickel sulfide which has beendeteriorated by non-halogen containing deposits, which comprisestreating said catalystwith a gas mixture comprising sulfur dioxide andhydrogen sulfide at a temperature between about 400 C. and 600 C.

RAYMOND C. ARCHIBALD.

